// It randomly fetches an IP via custom LookupHost function and dials it by the given dial
// function. LookupHost may implement an internal DNS caching implementation, lookupHost
// input if nil then net.DefaultResolver.LookupHost is used.
//
// It dials one by one and returns first connected `net.Conn`.
// If it fails to dial all IPs from cache it returns first error. If no baseDialFunc
// is given, it sets default dial function.
//

// determine that value and use it in the "expected" results for the test
// cases in TestResolveAddr(). Need to wrap IPv6 addresses in square
// brackets.
func determineLocalHostIPString(t *testing.T) string {
	ips, err := net.DefaultResolver.LookupNetIP(context.Background(), "ip", "localhost")
	if err != nil || len(ips) == 0 {
		t.Fatalf("Test setup failure - unable to determine IP of localhost: %v", err)
	}
	var ret string
	for _, ip := range ips {

	if err != nil {
		return nil, err
	}
	switch afnet {
	case "ip", "ip4", "ip6":
	default:
		return nil, UnknownNetworkError(network)
	}
	addrs, err := DefaultResolver.internetAddrList(context.Background(), afnet, address)
	if err != nil {
		return nil, err
	}
	return addrs.forResolve(network, address).(*IPAddr), nil
}

	if (len(lookupIPAddr) > 0) && (lookupIPAddr[0] != nil) {
		// if there are more than one lookup function, ignore all but first
		addrs, lookupErr = lookupIPAddr[0](ctx, host)
	} else {
		addrs, lookupErr = net.DefaultResolver.LookupNetIP(ctx, "ip", host)
	}
	if lookupErr != nil || len(addrs) == 0 {
		return "", fmt.Errorf("lookup failed for IP address: %w", lookupErr)
	}
	var resolvedAddr string

	for _, addr := range addrs {

	return &url.URL{Scheme: schemeReq, Host: net.JoinHostPort(info.Hostname, portReq)}, proxyTransport, nil
}

func isProxyableHostname(ctx context.Context, hostname string) error {
	resp, err := net.DefaultResolver.LookupIPAddr(ctx, hostname)
	if err != nil {
		return err
	}

	if len(resp) == 0 {
		return fmt.Errorf("no addresses for hostname")
	}
	for _, host := range resp {

			server := server
			var name string
			if def {
				name = "default/"
			} else {
				name = "go/"
			}
			t.Run(name+server, func(t *testing.T) {
				t.Parallel()
				r := DefaultResolver
				if !def {
					r = &Resolver{PreferGo: true}
				}
				fn(t, r, server)
			})
		}
	}
}

func TestNSLookupMX(t *testing.T) {
	testenv.MustHaveExternalNetwork(t)